to Stimuli in Corals 165 



been swallowed. Every mouth that was tested could thus take in 

 particles of meat. The touch of the food-particle on the oral disc 

 was also a stimulus for the expansion of the tentacles around the 

 mouth and of those around the neighbouring oral openings. 



When a particle of meat was placed on the tentacles of a colony 

 of Mceandra labyrinthiformis (Linn.), it was slowly passed on to the 

 oral disc, but the tentacles did not show any sign of contraction. 

 At the same time, the oral disc was depressed and arched over the 

 mouth opening till finally its margin closed over the peristome. In 

 the meantime, the tentacles were fully distended, the entocoelic 

 ones were directed obliquely towards the oral opening, those of 

 one side passing between those of the opposite side. The food- 

 particle was now hidden from view. After it had passed into the 

 ccjelenteric cavity and had presumably undergone partial digestion, 

 the periphery of the oral disc gradually moved outwards carrying 

 the tentacles with it, thus again exposing the peristomial cavity. 



The principal movements in these two cases are: 



(1) Ciliary movement passing the food-particle into the nearest 

 oral aperture. 



(2) The direction of the oral lip towards the food-particle pari 

 passu with the dilatation of the mouth. 



(3) The narrowing and deepening of the peristomial cavity, 

 which help to roll the food-particle into the oral opening. 



(4) The expansion of the tentacles of the affected oral disc and 

 of those of adjacent oral discs. 



(5) The eversion of the stomodeeum and consequent exposure 

 of the coelenteric cavity and mesenterial coils. 



(6) The return of the soft parts to their original condition by 

 the retraction of the stomodseum into the coelenteric cavity, recoil 

 of the oral lip to its normal extent, shortening of the tentacles, 

 flattening of the oral disc and withdrawal of its periphery carrying 

 the tentacles outwards. 



When a drop of meat-juice was gently placed on a colony of 

 Favia frag am (Esp.), the oral apertures in the neighbourhood were 

 slowly distended after a short pause. The inner or entocoelic row of 

 tentacles was then extended and directed over the oral disc, meeting 

 or intercrossing over the mouth as had been noticed in the case of 

 Mceandra labi/rinthiformis (Linn.), thus hiding the oral region, 

 whilst the exocoelic tentacles were arched outwards. Similar move- 

 ments were observed in Mceandra strigosa (Dana). 



When meat-juice was spurted by a pipette on sea- water con- 

 taining a colony of Orhicella cavernosa (Linn.), strong contraction 

 of the soft parts was set up in the neighbourhood, the polyps en- 

 tirely closing up. This was followed by the protrusion of convolutions 

 of mesenteries through mouth openings, oral discs and especially 

 through edge-zones, combined with secretion of mucus over the 

 polyps, the former obviously to paralyse prey and the latter to 



